Optical access networks connect subscribers of high bandwidth telecommunication services to their providers. Because of its high dependency on building access and infrastructure, the best performing, all optical, fiber to the home (FTTH) model has problems being accepted by the market, in particular since a possible bandwidth of up to 100 Gb/s is often not needed. Fiber to the cabinet (FTTC) is a much more cost-efficient model. It connects the existing street cabinet of the legacy copper cable infrastructure with optical fibers to a central office. The cabinets are equipped with optical network units (ONU) that perform the opto-electrical conversion and VDSL modems. The subscriber's VDSL modems are connected to the cabinets using the legacy copper infrastructure. In this model, the distance of the cabinets to the subscribers which is usually lower than 400 m limits the possible bandwidth to 50-100 Mb/s.
Another technology is based on the fiber to the distribution point (FTTdp) architecture and brings the fiber optic cable closer to the subscriber than the technology based on fiber to the cabinet (FTTC) architecture, but still uses the existing copper cable infrastructure for the last 100 m from a fiber distribution point to a subscriber. It is assumed that in the future the FTTdp architecture will be the favoured technology for optical access networks, since it allows increased bandwidth but still no optical fiber has to be employed in the building infrastructure.
However, the FTTdp architecture also brings challenges for the active distribution point equipment (DPE). The distribution point is the place in the optical network at which a subsequent fiber optic cable usually coming from an optical splitter at which a main fiber optic cable coming from the provider/central office is split to different ones of the subsequent fiber optic cable is coupled to an electrical cable of the legacy copper cable infrastructure. The electrical cable is connected to the home of the subscriber. The distribution point equipment is provided in a distribution point unit.
Instead of using large scale environmentally protected cabinets as usually utilized for housing the Distribution Point Equipment (DPE) in the fiber to the cabinet (FTTC) architecture, in case of the fiber to the distribution point (FTTdp) model, the equipment is deployed in much rougher and size-constrained environmental conditions like handholds. The usage of hardened fiber optical connectors (HFOC) providing sufficient water—and thus protection—is mandatory for every outside plant (OSP) environment. However, some of the active electronic devices, for example microchips, incorporated in a distribution point unit also require proper thermal management which is a major challenge because of size constraints.
Heat removal from electronic components that are deployed in protected environments mostly relies on natural or forced convection of air through a finned heat exchange body. The input air gets heated in a heat-exchanger and is removed away from the heat source. However, in a buried underground deployment scenario with sealed enclosures as the distribution point unit in a fiber to the distribution point network, air exchange is not possible so that convective heat dissipation is not very efficient.
It is desired to provide a distribution point unit for coupling an external electrical and optical cable that allows the processing of opto-electrical signals as well as cable routing and fiber splice protection functionality in a small constructed space and provides an efficient heat dissipation.